Fig. 2: Postprandial response of formulas predominantly containing α-lactalbumin or β-lactoglobulin as major whey proteins affecting tryptophan metabolism, using blood samples drawn from the cephalic vein.

A, B Levels of total essential amino acids (EAA) and the tryptophan to other large neutral amino acid (LNAA) ratio at baseline and at 30, 60, and 120 min post-meal. EAA measured include histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. LNAA includes isoleucine, leucine, valine, phenylalanine, and tyrosine. GC-MS-based untargeted metabolomics data were used. C–E Concentrations of tryptophan, kynurenine, and serotonin at baseline and at 30, 60, and 120 min post-meal. GC-MS-based targeted metabolomics data were used. A–E For the ALAC group, the number of samples analyzed at each time point was: baseline (n = 10), 30 min (n = 9), 60 min (n = 10), and 120 min (n = 6). For the WPI group: baseline (n = 10), 30 min (n = 8), 60 min (n = 10), and 120 min (n = 9). Data are represented as mean ± SEM. The significant differences between the ALAC and WPI groups were evaluated cross-sectionally using ANOVA on generalized log-transformed data, with litter effects accounted for in the model. *p < 0.05. F Postprandial tryptophan response by piglet using 4 repeated measures. Results were adjusted by baseline tryptophan level. Unadjusted results are presented in Supplementary Fig. 5. Formula intake for ALAC piglets is shown. G Pearson’s correlation demonstrates a strong positive correlation between tryptophan intake and serum tryptophan levels at 120 min post-meal.